1. Field of the Invention
The present invention relates in general to a scroll housing structure of a blower, and more particularly to a scroll housing structure of a multiblade blower suitable for lowering air noise and preventing flow loss.
2. Description of the Prior Art
With reference to FIGS. 1 and 2, there is shown a scroll housing structure of a multiblade blower in accordance with the prior art. The scroll housing structure includes an involute scroll casing 1 of which the upper section communicates with a delivery port 1a and the side wall has a suction port 1b. Through the suction port 1b, the outside air is introduced to the inside of the scroll casing 1 as will be described herein later. The scroll housing structure further includes an impeller 2 which is provided in the scroll casing 1 in such a manner that it is rotatably mounted on the center of the scroll casing 1. In order to rotate this impeller 2, an output shaft of a drive motor 2a is connected to the center of the impeller 2 to transmit its rotational force thereto. The impeller 2 is provided with a plurality of blades 2b arranged on the circumferential surface of the impeller 2.
The scroll casing 1 makes an acute angle with the delivery port 1a at a position where the involute of the scroll casing 1 starts. Hereinbelow, the position at which the casing 1 makes the acute angle with the delivery port 1a is named as an acute section 1c.
In operation, the impeller 2 is rotated about its center by the rotational force of the drive motor 1a. Such rotation of the impeller 2 generates a centrifugal force in the scroll casing 1. This forcibly introduces the outside air to the center of the impeller 2 in the scroll casing 1 through the suction port 1b of the casing 1. The air is in turn expelled from the rotating impeller 2 through the plurality of blades 2b provided on the circumferential surface of the impeller 2. The expelled air is, thereafter, delivered to the outside through the delivery port 1a.
In the above scroll housing structure, the pressure of the outside air, forcibly introduced to the center of the rotating impeller 2 due to the centrifugal force generated by the rotation of the impeller 2, increases while being expelled from the impeller 2 through the blades 2b. When the air is expelled from the impeller 2, the pressure of the air is substantially dynamic rather than static which is more desirable. In order to convert the dynamic pressure into the a static pressure, the scroll housing structure should be provided with the aforementioned involute scroll casing 1. Due to the involute scroll casing 1, the air, expelled from the rotating impeller 2 and passing by the acute section 1c of the casing 1 prior to flowing along the inner surface of the involute scroll casing 1, gradually recovers its static pressure while flowing along the inner surface of the involute scroll casing 1. The air recovering the static pressure is, thereafter, introduced to the delivery port 1a communicating with the upper section of the casing 1, and delivered to the outside or to a place requiring the air.
Turning to FIGS. 3 and 4, FIG. 3 is a speed diagram representing a flow speed of the air in the above scroll housing structure, and FIG. 4 is a sectional view of the scroll housing structure for showing the air streamlines of FIG. 3. Here, the outside air is introduced to the center of the impeller 2 in the scroll casing 1 and in turn pressurized by the centrifugal force generated by the rotation of the impeller 2, and flows along the inner surface of the scroll casing 1, as described above. When the air flows along the inner surface of the scroll casing 1, it forms streamlines as shown in FIGS. 3 and 4. In the FIG. 3, a flow speed of an air streamline is shown in a speed diagram at every predetermined point on the inner surface of the involute scroll casing 1. In FIG. 4, there are shown first and second streamlines A and B of the air expelled from the impeller 2 through the blades 2b as well as curvatures of the first and second streamlines A and B.
As shown in FIGS. 3 and 4, the streamline curvature of the outside air, forcibly introduced to the center of the rotating impeller 2 is increased due to the centrifugal force while passing through the blades 2b. Hence, the air undesirably flows along separated streamlines. That is, besides the first streamline A the air forms a second streamline B which is undesirably formed at a section near the suction port 1b, thus causing a flow loss. Moreover, the first streamline A or the primary streamline is curved to the side wall, on which the suction port 1b, is provided, thereby making the flow loss be worse.
The aforementioned problem starts to be prominently observed at a position corresponding to a line D (.THETA.=270.degree.) which is angularly spaced apart from a predetermined reference line C (.THETA.=0.degree.) of the scroll casing 1 by a predetermined angle.
In addition, the aforementioned increasing curvatures of the first and second streamlines A and B intensify the collision of the air against the inner surface of the scroll casing 1, thereby increasing the collision noise of the air. Another problem of the known scroll housing structure is resided in that the effective sectional area of the delivery port 1a of the scroll casing 1 is reduced and, as a result, a desired smooth recovery of the static pressure of the air is difficult to be achieved.